This is something I've wanted to do for a while but I never knew enough on how to implement it. I want to add walking with pokemon to an Advance gen game, like in HeartGold and SoulSilver. I know this would take a new ow table and some ASM coding most likely, but what I want to know is, can it be done? Even if it just started off simple like in Pokemon Yellow where your Pikachu never goes in its pokeball; just have it so your starter always walks with you. Any ideas would be great.

Last I checked, Jambo was working on a follow me routine, but he hasn't finished yet/released it to the public. It has not been discovered fully yet.

You can easily do scripts/routines to find out which pokemon you want to follow you...but the actual following part is what's hard.